When I was your age, I left the East Coast for Orange County, CA. Thought it was a 2-3 year experiment. 20 years later, here I am. Fabulous weather, many natural wonders of the country within a days drive, great running opportunities. San Diego and San Fran are similar. It is expensive.
I'd avoid the midwest like the black plague. Land locked, narrow minded people, harsh winters and you'll never find a thin girl.
Some other places I have been that I enjoyed enough to consider living:
Asheville, NC - trails, history, decent running community.
Richmond, VA - Smaller than Boston, less college influence, but good history, trails, running community. Affordable.
Colorado front range (C.Springs, Boulder, Fort Collins, Denver). Lots of sunny days, great running.
Santa Fe, NM - Albuquerque close by, but would not live there. Lots of running opportunity.